And we could install some cheap device in each cars to detect when a driver is tired and keep him awake, and detect a drunk driver and stop him drive or perform some other action.

Until most of people will afford a self driving car you would still have to face the drunk, or the ones that text so you will not remove those of the roads.

There are luxury cars that attempt to detect when a driver is falling asleep, and people are sometimes mandated to have an interlock on their cars that prevents starting if they have alcohol in their breath. So if these things are not universal, presumably it's because of cost-benefit analysis, not because they need to be invented.

I was involved back in 2003-2004 with an Australian company called SeeingMachines (I worked for a UK redistributor).

These guys made a remote video face-and-eye tracker that they sold to automotive companies wanting to research different dashboard designs -- they would look for blinks and head-nods to measure how fatigued a driver was, and to optimise the dashboard design to keep the driver awake.

I'm sure they are now selling their technology to automotive OEMs for placement in driver-facing camera ECUs.

Their technology worked OK back in 2003. I'm sure it is very robust and mature by now.

Not a bad idea.